1. Field of the Invention
The present invention relates to a high-pressure fuel pump used for an in-cylinder injecting type engine or the like, and more particularly, to a high-pressure fuel pump which permits minimization of the pulsation of the fuel pressure and stabilization of the quantity of injected fuel and the engine revolutions.
2. Description of the Related Art
As an engine of a type of injecting fuel in cylinders of the engine, referred to as the in-cylinder injecting type engine or the direct injecting type engine, there is widely known a diesel engine. An in-cylinder injecting type has recently been proposed even for a spark igniting engine (gasoline engine). In such an in-cylinder injecting type engine, there is a tendency toward increasing the fuel injecting pressure to a sufficiently high level of fuel injecting pressure of, for example, 50 atm. At the same time, the fuel pressure pulsation is required to be small for stabilization of injection. For these purposes, it has been the conventional practice to use a multi-cylinder high-pressure fuel pump having several plungers, such as one disclosed in Japanese Unexamined Patent Publication No. H08-158,974.
In such a multi-cylinder high-pressure fuel pump, however, the complicated structure results in a larger scale and hence in a higher manufacturing cost. Further, it is technically difficult to achieve satisfactory clearance matching applied to minimize fluctuations in accuracy between cylinders, requiring a further increase in the manufacturing cost. A single-cylinder type high-pressure fuel pump is therefore proposed. However, since there is only a single plunger, this type of fuel pump poses a problem of considerable pulsation of pressure of the discharged fuel, and it is necessary to stabilize pulsation at a low cost.